Thermoplastic elastomers step-growth polymerization

Abstract Polymers are macromolecules derived by the combination of one or more chemical units (monomers) that repeat themselves along the molecule. The lUPAC Gold Book defines a polymer as A molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. Several ways of classification can be adopted depending on their source (natural and synthetic), their structure (linear, branched and crosslinked), the polymerization mechanism (step-growth and chain polymers) and molecular forces (Elastomers, fibres, thermoplastic and thermosetting polymers). In this chapter, the molecular mechanisms and kinetic of polymer formation reactions were explored and particular attention was devoted to the main polymerization techniques. Finally, an overview of the most employed synthetic materials in biomedical field is performed. 

Anionic polymerization requires a type of monomer that contains an electron-withdrawing substituent such as phenyl, carboxyl, nitrile, and diene. Successful industrial examples are some styrenic products such as styrene-butadiene mbber (SBR) and styrene-butadiene-styrene (SBS) thermoplastic elastomer resins. Commonly used industrial catalysts are ethyl lithium (C2H5li) and sodium naphthalide (CioHgNa), which quickly dissolves and dissociates in a proper solvent. The primary anion R" reacts with monomer and initiates chain growth through successive propagation steps ... 

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